Drug interactions
Metoprolol + Quinidine
Severity: Major
Metoprolol and Quinidine: major interaction.
Last updated Sources: US FDA label
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Quinidine blocks CYP2D6 and markedly raises metoprolol levels, effectively making patients poor metabolizers. This can cause bradycardia, hypotension and loss of beta-1 selectivity.
What this interaction means in plain words
Metoprolol and Quinidine can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.
Metoprolol belongs to Cardiovascular; Quinidine belongs to Anti Parasitic.
Why it happens
CYP2D6 inhibition reduces metoprolol clearance.
What to do
Monitor heart rate and blood pressure closely and reduce the metoprolol dose as needed. Consider a beta-blocker not dependent on CYP2D6, such as atenolol or bisoprolol.
What to ask your pharmacist
- Does the benefit of taking both outweigh the risk in my case?
- Do I need any blood test, ECG or other check while on both?
- What early warning signs should I watch for, and what should I do if they appear?
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References
Other interactions of Quinidine
- Adagrasib + Quinidine Contraindicated
- Arsenic trioxide + Quinidine Contraindicated
- Artemether / lumefantrine + Quinidine Contraindicated
- Chloroquine + Quinidine Contraindicated
- Dofetilide + Quinidine Contraindicated
- Dronedarone + Quinidine Contraindicated
Other interactions of Metoprolol
- Metoprolol + Thioridazine Contraindicated
- Amifostine + Metoprolol Major
- Amiodarone + Metoprolol Major
- Atenolol-chlorthalidone + Metoprolol Major
- Atenolol + Metoprolol Major
- Betaxolol + Metoprolol Major
Frequently asked questions
Can I take Metoprolol with Quinidine?
MediHelp rates the interaction as major. Metoprolol and Quinidine can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. Quinidine blocks CYP2D6 and markedly raises metoprolol levels, effectively making patients poor metabolizers. This can cause bradycardia, hypotension and loss of beta-1 selectivity.
How serious is the interaction between Metoprolol and Quinidine?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor heart rate and blood pressure closely and reduce the metoprolol dose as needed. Consider a beta-blocker not dependent on CYP2D6, such as atenolol or bisoprolol.
What other medicines interact with Quinidine?
MediHelp also lists interactions of Quinidine with, for example, Adagrasib, Arsenic trioxide, Artemether / lumefantrine. The full list is on the Quinidine page.
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